U.S. patent application number 12/665661 was filed with the patent office on 2010-12-23 for data transmission/receiving method in multimedia broadcast multicast service system and apparatus thereof.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. Invention is credited to Seung-Chan Bang, Jae-Heung Kim, Jung-Im Kim, Kyoung-Seok Lee, Byung-Han Ryu.
Application Number | 20100325509 12/665661 |
Document ID | / |
Family ID | 40156411 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100325509 |
Kind Code |
A1 |
Kim; Jung-Im ; et
al. |
December 23, 2010 |
DATA TRANSMISSION/RECEIVING METHOD IN MULTIMEDIA BROADCAST
MULTICAST SERVICE SYSTEM AND APPARATUS THEREOF
Abstract
Provided is a Multimedia Broadcast Multicast Service (MBMS);
and, more particularly, a data transmission/receiving method in a
multimedia broadcast multicast service system, and an apparatus
thereof. The data transmitting method in the MBMS system includes
the step of checking a terminal receiving data provided from the
MBMS and the step of determining whether there is error report
feedback on retransmission of the data according to the number of
the detected terminals.
Inventors: |
Kim; Jung-Im; (Daejon,
KR) ; Lee; Kyoung-Seok; (Daejon, KR) ; Kim;
Jae-Heung; (Daejon, KR) ; Ryu; Byung-Han;
(Daejon, KR) ; Bang; Seung-Chan; (Daejon,
KR) |
Correspondence
Address: |
LAHIVE & COCKFIELD, LLP;FLOOR 30, SUITE 3000
ONE POST OFFICE SQUARE
BOSTON
MA
02109
US
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejon
KR
|
Family ID: |
40156411 |
Appl. No.: |
12/665661 |
Filed: |
June 20, 2008 |
PCT Filed: |
June 20, 2008 |
PCT NO: |
PCT/KR2008/003530 |
371 Date: |
December 18, 2009 |
Current U.S.
Class: |
714/750 ;
714/E11.131 |
Current CPC
Class: |
H04W 72/005 20130101;
H04L 1/1825 20130101; H04L 1/1685 20130101; H04L 1/1887 20130101;
H04L 2001/0093 20130101 |
Class at
Publication: |
714/750 ;
714/E11.131 |
International
Class: |
H04L 1/14 20060101
H04L001/14; H04L 1/18 20060101 H04L001/18; G06F 11/14 20060101
G06F011/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2007 |
KR |
10-2007-0060396 |
Claims
1. A data transmitting method in a Multimedia Broadcast Multicast
Service (MBMS) system, comprising: detecting terminals receiving
data provided from the MBMS; and determining whether there is error
report feedback on transmission retransmission of the data
according to the number of the detected terminals.
2. The data transmitting method of claim 1, wherein said detecting
a terminal receiving data includes: transmitting to a terminal a
polling request message for requesting polling of checking whether
to receive the data provided from the MBMS; and receiving a polling
response message for polling response to the polling request
message from the terminal.
3. The data transmitting method of claim 2, wherein the polling
response is made using an identifier.
4. The data transmitting method of claim 3, wherein the identifier
is defined based on a time cycle of the polling and a time interval
of the polling response.
5. The data transmitting method of claim 2, wherein the
determination is made comparing the number of the terminals
detected receiving data with a preset value.
6. The data transmitting method of claim 5, wherein the
determination is made through: when the number of the detected
terminals is larger than the preset value, adopting a
retransmission method without error report feedback to transmit
data repeatedly and determining a channel for feedback as a channel
for receiving the polling response message; and when the number of
the detected terminals is smaller than the preset value, adopting a
retransmission method with error report feedback for data
retransmission and determining the channel for feedback as a
channel for receiving the error report.
7. The data transmitting method of claim 6, wherein the preset
value is set up based on the amount of retransmitted data according
to whether or not there is the error report feedback.
8. The data transmitting method of claim 6, wherein when the number
of the detected terminals is larger than the preset value, data
retransmission is performed on the entire data according to the
determined retransmission method; and when the number of the
detected terminals is smaller than the preset value, retransmission
is performed on the data reported to have an error according to the
determined retransmission method.
9. The data transmitting method of claim 6, wherein a cyclic
redundancy check (CRC) method is adopted for the error report.
10. The data transmitting method of claim 1, wherein Hybrid
Automatic Repeat reQuest (HARQ) mechanism is adopted for the data
transmission retransmission.
11. A data receiving method in a Multimedia Broadcast Multicast
Service (MBMS) system, comprising: checking whether to receive data
provided from the MBMS; and controlling a feedback channel based on
control information including feedback channel information
according to whether or not there is error report feedback on
retransmission of the data determined according to the number of
the terminals detected to receive the data.
12. The data receiving method of claim 11, wherein said checking
whether to receive data includes: receiving a polling request
message for requesting polling of checking whether to receive the
data provided from the MBMS; and transmitting a polling response
message for polling response to the polling request message to a
base station.
13. The data receiving method of claim 12, wherein the polling
response is made using an identifier.
14. The data receiving method of claim 13, wherein the identifier
is defined based on a time cycle of the polling and a time interval
of the polling response.
15. The data receiving method of claim 12, wherein the
determination is made by comparing the number of the terminals
checked receiving the data with a preset value.
16. The data receiving method of claim 15, wherein said controlling
a feedback channel includes: when the number of the terminals
receiving the data is larger than the preset value, adopting a
retransmission method without error report feedback for
retransmission of the data and using the feedback channel as a
channel for transmitting the polling response message; and when the
number of the detected terminals is smaller than the preset value,
adopting a retransmission method with error report feedback for
retransmission of the data and using the feedback channel as a
channel for transmitting the error report.
17. The data receiving method of claim 16, wherein the preset value
is set up based on the amount of retransmitted data according to
whether or not there is an the feedback.
18. The data receiving method of claim 16, wherein when the number
of the detected terminals is larger than the preset value,
retransmission is performed on the entire data according to the
determined retransmission method; and when the number of the
detected terminals is smaller than the preset value, retransmission
is performed on the data reported to have an error according to the
determined retransmission method.
19. The data receiving method of claim 16, wherein a cyclic
redundancy check (CRC) method is adopted for the error report.
20. The data receiving method of claim 11, wherein Hybrid Automatic
Repeat reQuest (HARQ) mechanism is adopted for the
retransmission.
21-30. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a Multimedia Broadcast
Multicast Service (MBMS); and, more particularly, to a data
transmission/reception method in a multimedia broadcast multicast
service system, and an apparatus thereof.
BACKGROUND ART
[0002] A Multimedia Broadcast Multicast Service (MBMS) is
multimedia broadcast and multicast service in a 3rd Generation
Partnership Project (3GPP) wireless communication system. The MBMS
service adopts a method for simultaneously transmitting data in
multi-cell. The multi-cell transmit data in order to lower an error
rate by combining a plurality of signals transmitted in different
cells.
[0003] In case of Release-6 MEMS of 3GPP, data are transmitted from
a plurality of cells. However, since a 3GPP Release-6 system is an
asynchronous system, it cannot simultaneously receive the data
transmitted from a terminal even if data are transmitted from a
plurality of cells. Accordingly, there is a difficulty that the
terminal should independently receive and combine signals
transmitted from each cell. Although a plurality of errors occur
due to a poor channel state, the terminal does not report the
errors and data are not retransmitted. In order to lower the error
rate, data repetition is performed in an application layer. The
data transmission repetition is performed without feedback on a
radio channel from the terminal. Accordingly, there is a problem in
that data transmission repetition is performed while wasting radio
resources even in a situation that data transmission repetition is
not required.
[0004] In a 3GPP Long Term Evolution (LTE) MEMS service which is
introduced after Release-6 and Release-7, when MBMS is serviced in
the multi-cell, the cells transmit the same contents
simultaneously.
[0005] In the multi-cell transmission, it is possible to lower the
error rate by providing the terminal with reception signals of a
higher strength than that of signals for a single cell. However,
the low error rate is not provided to all the terminals within the
entire coverage of the multi-cell. That is, it is difficult to
expect the low error rate in case of terminals having a large cell
radius and located in cell boundaries, and a terminal of a cell
located in the boundary of multi-cell, not at the center of the
multi-cell. On the other hand, it is easy to expect the low error
rate in cells having a small radius and located at the center of
the multi-cell. Therefore, when the radio channel environment is
poor in the multi-cell transmission, a method for reducing a packet
error rate is required. Accordingly, when an error occurs, it is
required to retransmit the data.
[0006] The 3GPP Release-6 and Release-7 systems perform counting
and recounting to check the existence of the terminal receiving the
MEMS service. During counting and recounting procedures, the
terminal hoping to receive MEMS service should response through
Random Access Channel. In the Release-6 and 7 systems, a
controlling radio network controller (C-RNC) controls interference
caused by excessive random access between terminals by notifying
probability information that the terminal should respond to the
counting through the random access channel for counting and
recounting.
[0007] The 3GPP LTE MBMS service performs polling, which is simpler
than the counting and recounting in order to check whether there is
a terminal receiving the MBMS data in the cell. However, there is a
problem in that a polling procedure and a feedback channel for
performing polling are not defined.
DISCLOSURE
Technical Problem
[0008] An embodiment of the present invention is directed to
raising efficiency of retransmission for correcting an error
occurring in a radio channel, e.g., Hybrid Automatic Repeat reQuest
(HARQ), when a wireless communication system simultaneously
performs broadcast and multicast services in multi-cell.
[0009] Another embodiment of the present invention is directed to
providing a polling method of methods for checking whether there is
a terminal receiving a service and a method for operating a
feedback channel which is required to perform retransmission for
correcting an error occurring in a radio channel.
[0010] Other objects and advantages of the present invention can be
understood by the following description, and become apparent with
reference to the embodiments of the present invention. Also, it is
obvious to those skilled in the art of the present invention that
the objects and advantages of the present invention can be realized
by the means as claimed and combinations thereof.
Technical Solution
[0011] In accordance with an aspect of the present invention, there
is provided a data transmitting method in a Multimedia Broadcast
Multicast Service (MBMS) system, includes: checking a terminal
receiving data provided from the MBMS; and determining whether
there is error report feedback on retransmission of the data
according to the number of the detected terminals.
[0012] In accordance with another aspect of the present invention,
there is provided a data receiving method in an MBMS system,
including: checking whether to receive data provided from the MEMS;
and controlling a feedback channel based on control information
including feedback channel information according to whether or not
there is error report feedback on retransmission of the data
determined according to the number of the detected terminals.
[0013] In accordance with another aspect of the present invention,
there is provided a data transmitting apparatus in an MBMS system,
including: a communication unit for checking a terminal receiving
data provided from the MBMS; and a control unit for determining
whether or not there is an error report feedback on retransmission
of the data according to the number of the detected terminals.
[0014] In accordance with another aspect of the present invention,
there is provided a data receiving apparatus in an MBMS system,
including: a communication unit for checking whether to receive
data provided from the MBMS; and a control unit for controlling a
feedback channel based on control information including feedback
channel information according to whether or not there is error
report feedback on retransmission of the data determined according
to the number of the detected terminals.
[0015] The advantages, features and aspects of the invention will
become apparent from the following description of the embodiments
with reference to the accompanying drawings, which is set forth
hereinafter. Therefore, those skilled in the art of the present
invention can embody the technological concept and scope of the
invention easily. In addition, if it is considered that detailed
description on a related art may obscure the points of the present
invention, the detailed description will not be provided herein.
Specific embodiments of the present invention will be described in
detail hereinafter with reference to the attached drawings.
ADVANTAGEOUS EFFECTS
[0016] The present invention can efficiently use radio resources by
preventing unnecessary data repetition.
[0017] Also, the present invention can efficiently use radio
resources by in a neighboring cell operating different
retransmission methods according to the number of terminals
receiving data to thereby prevent large interference from occurring
and preventing unnecessary data retransmission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a flowchart describing a Multimedia Broadcast
Multicast Service (MBMS) data transmitting/receiving method in
accordance with an embodiment of the present invention.
[0019] FIG. 2 shows a signal transmission procedure between a base
station and a terminal when there are a large number of terminals
accepting signal reception in accordance with an embodiment of the
present invention.
[0020] FIG. 3 shows a signal transmission procedure between the
base station and the terminal when there are a small number of
terminals accepting signal reception in accordance with an
embodiment of the present invention.
BEST MODE FOR THE INVENTION
[0021] Following description exemplifies only the principles of the
present invention. Even if they are not described or illustrated
clearly in the present specification, one of ordinary skill in the
art can embody the principles of the present invention and invent
various apparatuses within the concept and scope of the present
invention. The use of the conditional terms and embodiments
presented in the present specification are intended only to make
the concept of the present invention understood, and they are not
limited to the embodiments and conditions mentioned in the
specification.
[0022] In addition, all the detailed description on the principles,
viewpoints and embodiments and particular embodiments of the
present invention should be understood to include structural and
functional equivalents to them. The equivalents include not only
currently known equivalents but also those to be developed in
future, that is, all devices invented to perform the same function,
regardless of their structures.
[0023] For example, block diagrams of the present invention should
be understood to show a conceptual viewpoint of an exemplary
circuit that embodies the principles of the present invention.
Similarly, all the flowcharts, state conversion diagrams, pseudo
codes and the like can be expressed substantially in a
computer-readable medium, and whether or not a computer or a
processor is described distinctively, they should be understood to
express various processes operated by a computer or a
processor.
[0024] Functions of various devices illustrated in the drawings
including a functional block expressed as a processor or a similar
concept can be provided not only by using hardware dedicated to the
functions, but also by using hardware capable of running proper
software for the functions. When a function is provided by a
processor, the function may be provided by a single dedicated
processor, single shared processor, or a plurality of individual
processors, part of which can be shared.
[0025] The apparent use of a term, `processor`, `control` or
similar concept, should not be understood to exclusively refer to a
piece of hardware capable of running software, but should be
understood to include a digital signal processor (DSP), hardware,
and ROM, RAM and non-volatile memory for storing software,
implicatively. Other known and commonly used hardware may be
included therein, too.
[0026] In the claims of the present specification, an element
expressed as a means for performing a function described in the
detailed description is intended to include all methods for
performing the function including all formats of software, such as
combinations of circuits for performing the intended function,
firmware/microcode and the like. To perform the intended function,
the element is cooperated with a proper circuit for performing the
software. The present invention defined by claims includes diverse
means for performing particular functions, and the means are
connected with each other in a method requested in the claims.
Therefore, any means that can provide the function should be
understood to be an equivalent to what is figured out from the
present specification.
[0027] The advantages, features and aspects of the invention will
become apparent from the following description of the embodiments
with reference to the accompanying drawings, which is set forth
hereinafter. Therefore, those skilled in the field of this art of
the present invention can embody the technological concept and
scope of the invention easily. In addition, if it is considered
that detailed description on a related art may obscure the points
of the present invention, the detailed description will not be
provided herein. The preferred embodiments of the present invention
will be described in detail hereinafter with reference to the
attached drawings.
[0028] The present invention checks a terminal receiving data of
Multimedia Broadcast Multicast Service (MBMS) in a cell and
determines presence of error report feedback on retransmission for
correcting an error occurring in a radio channel according to the
number of the terminals receiving data.
[0029] A polling method is adopted to check the terminal receiving
MBMS data in the cell. The polling is performed to search a
terminal interested in the MBMS data in the current cell to thereby
avoid unnecessary MBMS transmission. The terminal performs polling
response to a polling request for checking whether MBMS data
reception is required.
[0030] When it is checked that the number of terminals receiving
the MBMS data in the cell or an MBMS over Single Frequency Network
(MBSFN) region is large, a retransmission method without the error
report feedback is selected as a retransmission method for
correcting the error occurring in the radio channel. It is because
there is a possibility to perform retransmission to a large number
of terminals and a strong interference signal is given to a
neighboring cell due to increase of the error report feedback for
requesting retransmission from the terminal, i.e., feedback for
requesting retransmission due to the errors of the received MBMS
data, when there are a large number of terminals receiving the MBMS
data.
[0031] When it is checked that there are a large number of
terminals receiving the MBMS data, a base station notifies a
retransmission without error report feedback, reception information
on a selected channel and time to the terminal.
[0032] On the other hand, when it is checked that there are a few
terminals receiving the MBMS data in the cell or MBSFN region, a
retransmission method with error report feedback is selected as a
retransmission method for correcting the error occurring in the
radio channel. Since there are a few signals of feedback requesting
retransmission from the terminal in case where there are a few
terminals receiving the MBMS data, a possibility to give large
interference to the neighboring cell is low. Meanwhile, when it is
checked that there are a few terminals receiving the MEMS data and
retransmission is performed with error report feedback, a feedback
channel for retransmission is used as feedback of the terminal for
correcting the error occurring in the radio channel. The base
station notifies usage information on feedback channel to the
terminal through the control channel.
[0033] Accordingly, radio resources can be efficiently operated by
performing retransmission only on the data having an error and
preventing unnecessary retransmission. This will be described in
detail with an embodiment hereinafter.
First Embodiment
Data Transmitting Method in MBMS System
[0034] A data transmitting method in an MBMS system in accordance
with the present invention includes the steps of checking a
terminal receiving data provided in the MEMS and determining
presence of error report feedback on data retransmission according
to the number of detected terminals.
[0035] FIG. 1 is a flowchart describing an MBMS data
transmitting/receiving method in accordance with an embodiment of
the present invention and will be described with reference to FIG.
1.
[0036] A system starts in a cell at step S101. The cell includes a
multi-cell. A base station, i.e., eNode B, transmitting an MBMS
service in a 3rd Generation Partnership Project Long Term Evolution
(3GPP LTE) system is divided into a base station for transmitting a
unicast service and an MBMS service and a base station for
transmitting only the MBMS service. The former is a mixed cell and
the latter is a dedicated cell. In case of the mixed cell, the base
station performs the unicast and MEMS services at a predetermined
frequency band and transmits the unicast and MEMS services,
respectively according to each time. The dedicated cell performs
only the MBMS service at one frequency band.
[0037] While the service is provided since before the MBMS service
is started, each cell is checked at step S102 whether there is a
terminal receiving MEMS data in the cell. The step of checking
reception of the MEMS data includes the step of transmitting a
polling request message to the terminal in order to check whether
the base station is to receive the MBMS data and the step of
transmitting a polling response message to the base station as a
response to the polling request message. The polling method is one
of the methods for checking whether there are terminals receiving
any kinds of services. When the terminal does not respond to the
polling response message as a meaning that the terminal refuses to
receive the data provided from the MBMS, the base station
determines at step S103 whether to transmit the MBMS data based on
no response. Reversely, when the terminal inputs a reception
acceptance message of receiving the MBMS data in the polling
response message, the base station checks the terminal transmitting
the reception acceptance message with respect to the MBMS data.
[0038] Since a large number of terminals transmit the polling
response message in the present invention, polling response is
performed using an identifier of the terminal. The identifier is
defined based on a time cycle of polling and a time interval of
polling response. For example, the terminal identifier defines a
predetermined time cycle (P) corresponding to a polling cycle and a
time interval (T) of a channel for polling response by performing a
modular (%) operation as P/T. In this case, when P is 10 s and the
terminal polling response cycle is 100 ms, polling response, i.e.,
feedback for polling request, is performed for each time of
terminal identifier % 100 (10 s/100 ms).
[0039] It is determined at step S104 according to the number of
terminals checked by the reception acceptance message whether there
is error report feedback on MBMS data retransmission. The error
report feedback on retransmission means feedback for requesting
retransmission since there is an error in the received MBMS data.
The retransmission of the MBMS data means to retransmit the
pre-transmitted data to correct the error occurring due to poor
environment of the radio channel such as a Hybrid Automatic Repeat
reQuest (HARQ) method.
[0040] A strong interference signal may be generated in the
neighboring cell in case that when there are a large number of
terminals receiving the MBMS data, a large number of terminals
transmit the error report feedback for requesting retransmission to
the base station. On the other hand, since a few terminals transmit
the error report feedback for requesting retransmission to the base
station in case that there are a few terminals receiving the MBMS
data, it is possible to prevent generation of the strong
interference signal in the neighboring cell. Therefore, the present
invention can efficiently use radio resources by determining
whether there is error report feedback of the terminal for
retransmission of MBMS data according to the number of terminals
receiving the MBMS data.
[0041] When there are a large number of terminals receiving the
MBMS data, the retransmission method without error report feedback
is determined at step S105 for retransmission of the MEMS data.
When there are a large number of terminals receiving the MBMS data,
there is a possibility that the number of terminals receiving the
MBMS data including errors increases. In this case, since the
number of terminals transmitting the feedback for the error report
notifying that the error is included in the transmitted MBMS data
to the base station also increases, the strong interference signal
can be given to the neighboring cell. Accordingly, when there are a
large number of terminals receiving the MBMS data, the
retransmission method without feedback for error report is
selected. Since there is no feedback for error report, reception
acceptance message with respect to the MBMS data are transmitted by
using the polling response message at step S106. Accordingly, it
can be prevented to give the strong interference signal to the
neighboring cell. The retransmission method without error report
feedback is to perform retransmission on the MBMS data with respect
to the terminals where reception acceptance is checked.
[0042] That is, when the base station requests the terminal
according to the polling method whether to receive the MBMS data
and the number of responding terminals is sufficient, the base
station notifies a time for the terminal to respond to the polling
and probability information and receives polling response of the
terminal. The terminal feeds back polling response based on the
information notified by the base station. At this time, when a
signal-to-noise ratio (SNR) of the cell is low, i.e., when the
radio channel environment is poor, the base station performs
retransmission of the data to the terminals. When a large number of
terminals have a good radio channel environment but a few terminals
have a poor radio channel environment, retransmission is performed
on the entire terminals. Since polling is repeatedly performed, a
feedback channel is used as a channel for error report of
retransmission, not for polling response in case where the number
of terminals receiving the MBMS data decreases in a procedure of
transmitting the MBMS data and reaches a predetermined level, a
pre-set up value. At this time, it is unnecessary that the base
station equalizes radio resource locations of the error report
channel for hybrid retransmission and the channel for polling
response. The size and location of the feedback channel are
determined according to the number of terminals.
[0043] On the other hand, when the number of terminals receiving
the MBMS data is small, the retransmission method with the error
report feedback is determined at step S107 as a retransmission
method of the MBMS data. When the number of terminals receiving the
MBMS data is small, the number of terminals receiving the MBMS data
including errors is also small. In this case, although the feedback
for error report notifying that the error is included in the MBMS
data transmitted from the terminal is transmitted to the base
station, it does not lead to large interference in the neighboring
cell since the number of terminals transmitting feedback is small.
Meanwhile, the channel for feedback in the retransmission method
with the error report feedback is used as a channel for error
report at step S108.
[0044] Since the retransmission method with error report feedback
performs retransmission only on the MBMS data having errors, it is
possible to prevent unnecessary data retransmission.
[0045] That is, when the base station requests the terminal
according to the polling method whether to receive the MBMS data,
the base station determines to use the error report feedback
channel in case where the terminals are not sufficient, and
performs retransmission only in case where the terminal performs
error report. When the number of the error reports increases and
reaches the predetermined level, i.e., the preset value, the base
station determines not to use the error report feedback channel but
notifies the terminal to use the channel for transmitting the
polling response. At this time, the terminal performs feedback
based on the polling response time notified by the base station and
the probability information. In this case, the base station
performs retransmission on the entire data. The terminals receive
only the data having errors after retransmission.
[0046] A cyclic redundancy check (CRC) method is adopted for error
report and HARQ mechanism is adopted for retransmission.
[0047] Meanwhile, the number of terminals receiving the MBMS data
is determined by comparing the number of the terminal whose
reception acceptance is checked with the preset value described
above. The preset value is set up based on the retransmission
amount of the MBMS data according to whether there is feedback on
retransmission.
[0048] For example, a case that there are a large number of
terminals means a case that the number of terminals is larger than
the retransmission amount of the MBMS data in a state that there is
no error report, i.e., feedback, since retransmission is performed
on a plurality of MBMS data by reporting a plurality of errors in
the terminals when the base station allocates the feedback channel
for error report.
[0049] On the other hand, a case that there are a few terminals
means a case that the number of terminals is smaller than the
retransmission amount of the MBMS data in a state that there is no
error report, i.e., feedback, since retransmission is performed on
a small quantity of MBMS data by reporting a small number of errors
in the terminals when the base station allocates the feedback
channel for error report.
[0050] Meanwhile, a reference for selecting a feedback channel is
set up in consideration of efficiency of radio resources for each
base station. It is determined according to the reference whether
the feedback channel is used as a channel for polling response or a
channel for error report.
[0051] When the feedback channel is used only as the channel for
polling response, there is a benefit that neighboring cell
interference caused by feedback for error report of retransmission
does not occur. Also, when the feedback channel is used as the
channel for error report of retransmission, the base station checks
that the terminal exists through existence of the feedback channel.
It has a benefit that unnecessary retransmission is prevented by
performing retransmission only on the data having errors, not the
entire data.
[0052] A signal transmission procedure between the base station and
the terminal according to the number of terminals will be described
hereinafter.
[0053] FIG. 2 shows a signal transmission procedure between the
base station and the terminal in case where there are a large
number of terminals accepting signal reception in accordance with
an embodiment of the present invention and FIG. 3 shows a signal
transmission procedure between the base station and the terminal in
case where there are a small number of terminals accepting signal
reception in accordance with an embodiment of the present
invention.
[0054] 1. Case where there are a Large Number of Terminals
Accepting Signal Reception
[0055] Referring to FIG. 2, a base station 201 transmits a polling
request message to a terminal 202 (see 203). The terminal transmits
a polling response message to the base station as a response for
the polling request message (see 204). The base station 201 checks
a terminal accepting signal reception in the polling response
message transmitted from the terminal 202 and determines presence
of feedback on retransmission of the MBMS data according to the
number of terminals accepting signal reception. When there are a
large number of terminals accepting signal reception, the base
station 201 determines a data transmitting method as the method
without feedback error report on retransmission of the MBMS data.
The base station 201 transmits control information on transmission
of the polling response to the terminal 202 according to the
determined method (see 205). The terminal 202 receives control
information. The base station 201 transmits the MBMS data to the
terminal 202 (see 206). Although errors are included in the
received MBMS data, the terminal 202 does not report the error. The
base station 201 retransmits the MEMS data to the terminals
accepting signal reception (see 207). In a next polling procedure,
the terminal 202 transmits the polling response to the base station
201 through the feedback channel (see 208).
[0056] 2. Case where there are a Small Number of Terminals
Accepting Signal Reception
[0057] Referring to FIG. 3, a base station 301 transmits a polling
request message to the terminal 302 (see 303). The terminal
transmits a polling response message to the base station as a
response for the polling request message (see 304). The base
station 301 checks a terminal accepting signal reception in the
polling response message transmitted from the terminal 302 and
determines presence of error report feedback on retransmission of
the MBMS data according to the number of terminals accepting signal
reception. When there are a small number of terminals accepting
signal reception, the base station 301 determines a data
transmitting method as the method with feedback error report on
retransmission of the MBMS data. The base station 301 transmits to
the terminal 302 control information directing the terminal to use
the feedback channel for transmitting the error report according to
the determined method (see 305). The terminal 302 allocates the
channel for error report as a feedback channel. The base station
301 transmits the MBMS data to the terminal 302 (see 306). When the
received MBMS data include errors, the terminal 302 transmits the
error report to the base station 301 through the feedback channel
(see 307). The base station 301 retransmits the MBMS data only to
the terminals performing the error report (see 308).
Second Embodiment
Data Receiving Method in MBMS System
[0058] The data receiving method in a Multimedia Broadcast
Multicast Service (MBMS) system in accordance with another
embodiment of the present invention includes the step of checking
whether the data provided from the MBMS are received, and the step
of controlling a feedback channel based on control information
including feedback channel information according to whether or not
there is the error report feedback on retransmission of the data
determined by the number of the detected terminals. The HARQ
mechanism is adopted for retransmission.
[0059] The step of checking whether the data provided from the MBMS
are received includes the step of receiving a polling request
message for requesting polling of checking whether the data
provided from the MEMS is to be received, and the step of
transmitting a polling response message for polling response on the
polling request message to the base station. The polling response
is performed based on an identifier and the identifier is defined
based on a polling time cycle and a time interval of polling
response.
[0060] Determination is performed by comparing the number of the
reception detected terminals with the preset value. When the number
of detected terminals is larger than the preset value, the
retransmission method without error report feedback is determined
for data retransmission and the feedback channel is used as a
channel for transmitting the polling response message. When the
number of detected terminals is smaller than the preset value, the
retransmission method with error report feedback is determined for
data retransmission and the feedback channel is used as a channel
for transmitting the error report. The preset value is set up based
on the retransmission amount of data according to whether or not
there is feedback. When the number of detected terminals is larger
than the preset value, the determined retransmission method is to
perform data retransmission without remaining data. When the number
of detected terminals is smaller than the preset value, the
determined retransmission method is to perform retransmission only
on the data whose errors are reported. The cyclic redundancy check
(CRC) method is used for error report.
[0061] Since detailed description related to the present embodiment
is sufficiently provided in the first embodiment described above,
it will not be provided herein.
Third Embodiment
Data Transmitting Apparatus in MBMS System
[0062] The data transmitting apparatus in a Multimedia Broadcast
Multicast Service (MBMS) system in accordance with another
embodiment of the present invention includes a communication unit
for checking a terminal receiving data provided from the MBMS and a
control unit for determining whether there is error report feedback
on data retransmission according to the number of detected
terminals. Hybrid Automatic Repeat reQuest (HARQ) mechanism is
adopted for retransmission.
[0063] The communication unit includes a transmitting unit for
transmitting a polling request message of requesting polling for
checking whether to receive the data provided from the MBMS to the
terminal, and a receiving unit for receiving a polling response
message for polling response to the polling request message from
the terminal. The polling response is performed by an identifier.
The identifier is defined based on a time cycle of polling and a
time interval of polling response.
[0064] Determination is performed by comparing the number of
reception detected terminals with a preset value. When the number
of detected terminals is larger than the preset value, the
retransmission method without error report feedback is adopted for
data retransmission. A channel for feedback is used as a channel
for receiving the polling response message. When the number of
detected terminals is smaller than the preset value, the
retransmission method with error report feedback is adopted for
data retransmission and the channel for feedback is used as a
channel for receiving error report. The preset value is set up
based on the retransmission amount of data according to whether or
not there is feedback. When the number of detected terminals is
larger than the preset value, retransmission is performed on the
entire data according to the determined retransmission method. When
the number of detected terminals is smaller than the preset value,
retransmission is performed on the data reported to have an error
according to the determined retransmission method. The cyclic
redundancy check (CRC) method is adopted for error report.
[0065] Since detailed description related to the present embodiment
is sufficiently provided in the first embodiment described above,
it will not be provided herein.
Fourth Embodiment
Data Receiving Apparatus in MBMS System
[0066] The data receiving apparatus in Multimedia Broadcast
Multicast Service (MBMS) system in accordance with still another
embodiment of the present invention includes a communication unit
for checking whether to receive data provided from the MBMS, and a
control unit for controlling a feedback channel by receiving
control information including feedback channel information
according to whether or not there is error report feedback on
transmission retransmission of the data determined by the number of
detected terminals. Hybrid Automatic Repeat reQuest (HARQ)
mechanism is adopted for retransmission.
[0067] The communication unit includes a receiving unit for
receiving a polling request message for requesting polling of
checking whether to receive data provided from the MBMS, and a
transmitting unit for transmitting a polling response message for
polling response to the polling request message to the base
station. The polling response is performed by an identifier and the
identifier is defined based on a time cycle of polling and a time
interval of polling response.
[0068] Determination is performed by comparing the number of
reception detected terminals with a preset value. When the number
of detected terminals is larger than the preset value, the
retransmission method without error report feedback is adopted for
data retransmission. A channel for feedback is used as a channel
for transmitting the polling response message. When the number of
detected terminals is smaller than the preset value, the
retransmission method with error report feedback is adopted for
data transmission retransmission and the channel for feedback is
used as a channel for transmitting error report. The preset value
is set up based on the retransmission amount of data according to
whether or not there is feedback. When the number of detected
terminals is larger than the preset value, retransmission is
performed on the entire data according to the determined
retransmission method. When the number of detected terminals is
smaller than the preset value, retransmission is performed on the
data reported to have an error according to the determined
retransmission method. The cyclic redundancy check (CRC) method is
adopted for error report.
[0069] Since detailed description related to the present embodiment
is sufficiently provided in the first embodiment described above,
it will not be provided herein.
[0070] As described above, the technology of the present invention
can be realized as a program and stored in a computer-readable
recording medium, such as CD-ROM, RAM, ROM, floppy disk, hard disk
and magneto-optical disk. Since the process can be easily
implemented by those skilled in the art of the present invention,
further description will not be provided herein.
[0071] While the present invention has been described with respect
to certain preferred embodiments, it will be apparent to those
skilled in the art that various changes and modifications may be
made without departing from the scope of the invention as defined
in the following claims.
INDUSTRIAL APPLICABILITY
[0072] The present invention is applied to enhance operation
efficiency of a feedback channel related to retransmission in a
method and apparatus for transmitting/receiving MBMS data.
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